Discussion On Transforming The Runner By Adopting The Design Concept Of Flange Front Blade

For hydropower stations that have been put into operation for many years,the units have generally exposed problems such as low efficiency and poor hydraulic stability during operation.In addition,affected by various factors such as design,materials,and technology at the time,the problem of equipment aging has become increasingly serious,which has improved the safety and stability of the equipment.The operation poses a serious threat.At this stage,the improvement of the hydraulic performance of the turbine is mainly achieved through technical transformation,replacement of the turbine runner and water guide mechanism,or cutting of the exit edge of the blade.The conventional runner transformation method is to select a runner with a larger output in the model spectrum to match the original flow channel to increase the output of the unit.However,in recent years,numerical simulation technology has been widely used in the optimization design of hydraulic machinery,providing new solutions for the capacity expansion and transformation of hydraulic turbines Thoughts and directions.This article takes the Francis turbine of a small domestic hydropower station as the research object.Entrusted by the power station,the efficiency level and output capacity of the water turbine should be improved under the condition of only replacing the runner,and the vibration value of the unit should be reduced as much as possible.After the discussion of hydraulic parameters and the study of the design concept,it was finally decided to adopt a modified scheme of redesigning the runner,reducing the number of blades,and loading the front blades of the rim wing.This article first uses the component BLADEGEN-TURBOGRID-CFX in ANSYS WORKBENCH to design and calculate the runner with a single runner,and find the specific optimization direction of the blade in a short time.After repeated calculations on the single runner,the runner blade is initially established.The three-dimensional model of the blade is then further debugged in the numerical simulation of the full flow channel to finally establish the three-dimensional model of the blade.Then,numerical calculations of the full flow passage are carried out on the prototype turbine and the optimized turbine respectively,to verify the matching relationship between the new runner and the original flow passage,and to analyze and compare the hydraulic performance of the turbine before and after the transformation.Numerical calculations under ten working conditions prove that the turbine unit replacing the front-blade runner of the rim wing has better hydraulic performance.The hydraulic loss in the runner after the transformation is much smaller than that of the runner before the transformation,and After the transformation,the hydraulic loss of the runner continues to decrease with the increase of the guide vane opening.When the guide vane opening is 106.0mm,the hydraulic loss in the runner is only 3.34%.The reduction of the hydraulic loss can improve the energy utilization of the unit.rate.Except for small flow conditions,the efficiency of the transformed turbine is slightly lower than that of the original turbine.After the transformation,the power output and efficiency of the new turbines with other openings have been greatly improved.Under the optimal working condition of the prototype unit,the efficiency is 87.04% and the output is 1795.49 k W.Under this condition,the efficiency of the new-type unit is90.81%,the output is 2087.53 k W,the efficiency is increased by 3.77%,and the output is increased by 16.27%.With the replacement of runners,the optimal working condition of the new-type unit has shifted to large flow.The maximum efficiency of the new-type unit is 92.98% and the output is 2755.43 k W.At this opening,the efficiency of the prototype unit is 85.07% and the output is 2139.06 k W,under this opening degree,the new unit has a 7.91% increase in efficiency and a 28.81% increase in output compared to the original unit.In the case of a large opening of the guide vane,the pressure distribution of the front blade of the rim wing,the velocity vector situation,and the movement state of the internal streamline of the runner are smoother and more orderly than the original runner.The use of the runner after the transformation has greatly improved the internal flow state of the Francis turbine unit,and significantly improved the efficiency characteristics of the unit under non-design working conditions.